Many people seek skin treatment to improve the appearance of their skin, and particularly to reduce the discernible appearance of discolorations generally associated with aging. The skin conditions often targeted by such treatments include skin tags, moles, freckles, warts, actinic or seborrheic keratoses, angiomas and age spots (also known as liver spots), lentigines, or other skin-related abnormalities.
There are several types of procedures available that treat these skin conditions, ranging from topical ameliorations to more aggressive device treatments. Topical treatments include lotions, creams, acids, bleaching agents and vitamins. However, such treatments typically are slow, result in subtle improvement of the skin, may cause hypo- or hyper-pigmentation, and are often insufficient.
To provide a more complete treatment of the skin, it is known to use various optical device treatments (e.g., laser or other phototherapy). Such device treatments initially damage the target area, such that new skin proliferates after the healing process and generally improves the skin's appearance.
Optical device treatments typically include the use of lasers or other radiation to heat the skin or underlying tissue. For example, U.S. Patent Appl. No. 2008/0200908 to Domankevitz (publ. August 2008) discusses the use of the radiation to heat and thereby damage hair follicles. However, such radiation treatment can be painful for patients. In addition, such treatment is not precisely targeted to only treat the hair follicles. Instead, an area of skin with a plurality of hair follicles is flooded with the radiation until the follicles are damaged.
It is also known to use optical treatment devices to treat unwanted veins. For example, U.S. Pat. No. 5,522,813 to Trelles and U.S. Patent Appl. No. 2008/0071258 to Lemberg (publ. March 2008) discuss methods of treating veins using laser pulses laser to create holes or channels in the skin. However, such methods are problematic as they use the pulses to dig or pit into the skin, rather than attempt to dither (feather) the discoloration resulting from the treatments. In addition, such methods can leave scars on a patient.
Laser treatment devices have also been used to treat lesions. Such treatments are discussed in U.S. Patent Appl. No. 2007/0140426 to Axelrod (publ. June 2007), U.S. Patent Appl. No. 2007/0118098 to Tankovich (publ. May 2007), and U.S. Patent Appl. No. 2008/0009841 to Kuo (publ. January 2008).
The above laser treatments all suffer from similar disadvantages. Laser treatments often cause patients unnecessary pain or can scar the patient's skin. During laser treatment, scattering and absorption of the laser light often occurs in the skin tissue, which can cause significant changes in skin coloration and even scarring. In addition, laser treatments are often manually mediated, which can lead to mismatch of the flux of the laser to the spot. In addition, such manual mediation often leads to wide variation of treatment from one practitioner to the next.
To overcome some of the disadvantages of laser treatment, some practitioners currently use intense pulsed light (IPL) to treat lesions by damaging the unwanted tissue. An exemplary device is discussed in U.S. Patent Appl. No. 2008/0215124 to Wagenaar Cacciola, et al. (publ. September 2008). However, such IPL devices suffer from many of the disadvantages discussed above.
To avoid many of the disadvantages associated with optical treatment of the skin, various methods and device for cryogenic treatment are also known in the art, and such treatments generally involve the application of liquid nitrogen to a portion of the skin, such as by a spray or a cotton tipped applicator.
It has been reported that melanocytes freeze at −4 to −7° C. while surrounding squamous cells resist injury up to −20° C. Thus, it is possible to selectively treat lentigines without causing excessive damage to surrounding skin. When using cryogenic treatment, it is important to cool the treatment region to the proper temperature for an appropriate time. Cooling the region to too low a temperature can cause excessive damage. Cooling the region for too long a period of time can cause conduction of the cold temperature to neighboring tissue, increasing the size of the affected area. In addition, while surrounding tissue can survive a brief exposure to the very cold temperatures, prolonged exposure can cause tissue necrosis or excessive damage.
U.S. Pat. No. 6,226,996 to Weber et al. discusses a handheld device that includes a nozzle from which cryogenic fluid is sprayed on to the skin by a practitioner. The Weber device can be problematic as it simply sprays a cryogenic mist over the entire treatment area, which can lead to excessive or insufficient treating and cause hyper- or hypo-pigmentation of the skin. In addition, the Weber device requires manual movement and therefore lacks the ability to be positioned precisely over the desired treatment area, making it difficult to precisely control the temperature of the treatment area and surrounding skin, which often leads to inconsistent treatment.
U.S. Pat. No. 6,413,252 to Zavislan discusses a more complex treatment device that includes a confocal microscope to view sections of the treatment area. The area can be frozen by flooding the chamber above the area with a cryogenic fluid. However, the Zavislan device also utilizes a single pulse of cryogenic fluid to flood the entire treatment area, and suffers from the same problems as the Weber device discussed above.
Thus, there is still a need for a treatment apparatus that dispenses cryogenic fluid on a lesion at multiple regions of the lesion for a precise duration of time to cool the lesion and the surrounding skin to within a narrow temperature range.